Anatoliy Gorbenko

F(I)MEA-technique of web services analysis and dependability ensuring

Dependability analysis of the Web Services (WSs), dsclosure of possible failure modes and their effects are open problems. This paper gives results of the Web Services dependability analysis using standardized FMEA- (Failure Modes and Effects Analysis) technique and its proposed modification IMEA- (Intrusion Modes and Effects Analysis) technique. Obtained results of FMEA-technique application were used for determining the necessary means of error recovery, fault prevention, fault-tolerance ensuring and fault removal. Systematization and analysis of WS intrusions and means of intrusion-tolerance were fulfilled by use of IMEA-technique. We also propose the architectures of the fault and intrusion-tolerant Web Services based on the components diversity and dynamical reconfiguration as well as discuss principles and results of dependable and secure Web Services development and deployment by use of F(I)MEA-technique and multiversion approach.

Using Inherent Service Redundancy and Diversity to Ensure Web Services Dependability

Achieving high dependability of Service-Oriented Architecture (SOA) is crucial for a number of emerging and existing critical domains, such as telecommunication, Grid, e-science, e-business, etc. One of the possible ways to improve this dependability is by employing service redundancy and diversity represented by a number of component web services with the identical or similar functionality at each level of the composite system hierarchy during service composition. Such redundancy can clearly improve web service reliability (trustworthiness) and availability. However to apply this approach we need to solve a number of problems. The paper proposes several solutions for ensuring dependable services composition when using the inherent service redundancy and diversity. We discuss several composition models reflecting different dependability objectives (enhancement of service availability, responsiveness or trustworthiness), invocation strategies of redundant services (sequential or simultaneous) and procedures of responses adjudication.

Experimenting with exception propagation mechanisms in service-oriented architecture

Exception handling is one of the popular means used for improving dependability and supporting recovery in the Service-Oriented Architecture (SOA). This practical experience paper presents the results of error and fault injection into Web Services. We summarize our experiments with the SOA-specific exception handling features provided by the two development kits: the Sun Microsystems JAX-RPC and the IBM WebSphere Software Developer Kit for Web Services. The main focus of the paper is on analyzing exception propagation and performance as the major factors affecting fault tolerance (in, particular, error handling, and fault diagnosis) in Web Services.

Green computing and communications in critical application domains: Challenges and solutions

Information and communication technologies (IT) and IT-based instrumentation and control (I&C) systems, hardware and software components are analyzed in context of “green” paradigm. Green IT paradigm is formulated as a Cartesian product of a pair “external (E) and internal (I) aspects of IT and computer-based I&Csystems” and a pair “power (recourse) consumption minimization (Rmin) and safety maximization (Smax)”. In the paper we discuss main research challenges and development solutions, education and training activities in the domain of green and safe computing and communication. Finally, we report results of EU-TEMPUS projects in the area of safe and green ITs and define models of academia and industry cooperation for excellence, innovations and knowledge exchange.

The threat of uncertainty in service-oriented architecture

In this paper we present our practical experience in benchmarking a number of existing Web Services, and investigating the instability of their performance and the delays induced by the communication medium. We provide the results of statistical data analysis and discuss a technique of Web Services performance assessment taking out of the network delays. We have found that the uncertainty discovered in Web Services operations affects dependability of Service-Oriented Architecture and will require additional specific resilience techniques.

Applying F(I)MEA-technique for SCADA-Based Industrial Control Systems Dependability Assessment and Ensuring

Dependability and security analysis of the industrial control computer-based systems (ICS) is an open problem. ICS is a complex system that as a rule consists of two levels - supervisory control and data acquisition (SCADA) and programmable logic controllers (PLC) and has vulnerabilities on both levels. This paper presents results of the SCADA-based ICS dependability and security analysis using a modification of standardized FMEA (failure modes and effects analysis)-technique. The technique mentioned takes into account possible intrusions and is called F(I)MEA (failure (intrusion) modes and effects analysis). F(I)MEA-technique is applied for determining the weakest parts of ICS and the required means of fault prevention, fault detection and fault-tolerance ensuring. An example of F(I)MEA-technique applying for SCADA vulnerabilities analysis is provided. The solutions of SCADA-based ICS dependability improvement are proposed.

Dependable composite web services with components upgraded online

Achieving high dependability of Web Services (WSs) dynamically composed from component WSs is an open problem. One of the main difficulties here is due to the fact that the component WSs can and will be upgraded online, which will affect the dependability of the composite WS. The paper introduces the problem of component WS upgrade and proposes solutions for dependable upgrading in which natural redundancy, formed by the latest and the previous releases of a WS being kept operational, is used. The paper describes how ‘confidence in correctness’ can be systematically used as a measure of dependability of both the component and the composite WSs. We discuss architectures for a composite WS in which the upgrade of the component WS is managed by switching the composite WS from using the old release of the component WS to using its newer release only when the confidence is high enough, so that the composite service dependability will not deteriorate as a result of the switch. The effectiveness of the proposed solutions is assessed by simulation. We discuss the implications of the proposed architectures, including ways of ‘publishing’ the confidence in WSs, in the context of relevant standard technologies, such as WSDL, UDDI and SOAP.

Real Distribution of Response Time Instability in Service-Oriented Architecture

is paper reports our practical experience of benchmarking a complex System Biology Web Service, and investigates the instability of its behaviour and the delays induced by the communication medium. We present the results of our statistical data analysis and distributions which fit and predict the response time instability typical of Service-Oriented Architectures (SOAs) built over the Internet. Our experiment has shown that the request processing time of the target e-science Web Service (WS) has a higher instability than the network round trip time. It has been found that by using a particular theoretical distribution, within short time intervals the request processing time can be represented better than the network round trip time. Moreover, certain characteristics of the probability distribution series of the round trip time make it particularly difficult to fit them theoretically. The experimental work reported in the paper supports our claim that dealing with the uncertainty inherent in the very nature of SOA and WSs is one of the main challenges in building dependable service-oriented systems. In particular, this uncertainty exhibits itself through very unstable web service response times and Internet data transfer delays that are hard to predict. Our findings indicate that the more experimental data is considered the less precise distributional approximations become. The paper concludes with a discussion of the lessons learnt about the analysis techniques to be used in such experiments, the validity of the data, the main causes of uncertainty and possible remedial actions.

Exploring Uncertainty of Delays as a Factor in End-to-End Cloud Response Time

This paper reports our experience in benchmarking a cloud-based web-service and investigates instability of its performance and the delays induced by the communication medium when measured from multiple client locations. We compare the performance of MS Azure, Go Grid and an in-house server running the same benchmark web service and analyze how the client and service implementation technologies affect its performance. The uncertainty discovered in the network delay affects the overall performance and dependability of cloud computing provisioning and requires specific resilience techniques.

Using diversity in cloud-based deployment environment to avoid intrusions

This paper puts forward a generic intrusion-avoidance architecture to be used for deploying web services on the cloud. The architecture, targeting the IaaS cloud providers, avoids intrusions by employing software diversity at various system levels and dynamically reconfiguring the cloud deployment environment. The paper studies intrusions caused by vulnerabilities of system software and discusses an approach allowing the system architects to decrease the risk of intrusions. This solution will also reduce the so-called systems days-of-risk which is calculated as a time period of an increased security risk between the time when a vulnerability is publicly disclosed to the time when a patch is available to fix it.